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111.
The life cycle of the red alga Porphyra purpurea alternates between two morphologically distinct phases: a shell-boring, filamentous sporophyte and a free-living, foliose gametophyte. From a subtracted cDNA library enriched for sporophyte-specific sequences, we isolated a cDNA encoding an unusual elongation factor 1 (EF-1) that is expressed only in the sporophyte. A second EF-1 gene that is expressed equally in the sporophyte and the gametophyte was isolated from a genomic library. These are the only EF-1 genes detectable in P. purpurea. The constitutively expressed gene encodes and EF-1 very similar to those of most eukaryotes. However, the sporophyte-specific EF-1 is one of the most divergent yet described, with nine insertions or deletions ranging in size from 1 to 26 amino acids. This is the first report of a developmental stage-specific EF-1 outside of the animal kingdom and suggests a fundamental role for EF-1 in the developmental process. 相似文献
112.
Competition over mates takes many forms and has far-reaching consequences for many organisms. Recent work suggests that relative reproductive rates of males and females, sperm competition and quality variation among mates affect the strength of sexual selection. Song, other display, body size, visual ornaments and material resource offerings are often sexually selected. There is much empirical evidence of mate choice, and its evolution is clarified by mathematical models. Recent advances in theory also consider costs of choice, effects of deleterious mutations, fast and slow evolution of preferences and preferred traits, and simultaneous preferences for several traits. Contests over mates are important; so is sperm competition, scrambles, endurance rivalry, and coercion. The latter mechanisms have received less attention than mate choice. Sexual selection may explain puzzling aspects of plant pollination biology. 相似文献
113.
114.
Microtubule-associated proteins (MAPs) regulate microtubule stability and play critical roles in neuronal development and the balance between neuronal plasticity and rigidity. MAP1a (HGMW-approved symbol MAP1A) stabilizes microtubules in postnatal axons. We describe human MAP1a's genomic organization and deduced cDNA and amino acid sequences. MAP1a is a single-copy gene spanning 10.5 kb. MAP1a coding sequence is contained in five exons. Translation begins in exon 3. Human MAP1a contains 2805 amino acids (predicted molecular weight 306.5 kDa) and is slightly larger than rat MAP1a (2774 amino acids). Like rat and bovine MAP1a, human MAP1a contains conserved tubulin binding motifs in the amino-terminal region. The carboxy-terminal portion contains a conserved pentadecapeptide that is present in the light chain portion of rat and bovine MAP1a/LC2 polyprotein. We show that human MAP1a gene expression occurs almost exclusively in the brain and that there is approximately 10-fold greater gene expression in adult brain compared to fetal brain. Strong, interspecies conservation between human and rat MAP1a cDNA and amino acid sequences indicates important relationships between MAP1a's function and its primary amino acid sequence. 相似文献
115.
The inheritance of obesity has been analyzed in an intercross between the lean 129/Sv mouse strain and the obesity-prone EL/Suz mouse strain. The weights of three major fat pads were determined on 4-month-old mice, and the sum of these weights, divided by body weight, was used as an adiposity index. The strategy of selective DNA pooling was used as a primary screen to identify putative quantitative trait loci (QTLs) affecting adiposity index. DNA pools representing the leanest 15% and fattest 15% of the F2 progeny were compared for differential allelic enrichment using widely dispersed microsatellite variants. To evaluate putative QTLs, individual genotyping and interval mapping were employed to estimate QTL effects and assess statistical significance. One QTL affecting adiposity index, which accounted for 12.3% of phenotypic variance in gender-merged data, was mapped to the central region of Chromosome (Chr) 7. The QTL allele inherited from EL conferred increased adiposity. A second QTL that accounts for 6.3% of phenotypic variance was identified on Chr 1 nearD1Mit211.At both QTLs, the data are consistent with dominant inheritance of the allele contributing to obesity. The possible relationships between these QTLs and previously described obesity QTLs, major obesity mutations, and candidate genes are discussed. 相似文献
116.
Anders Kussak Barbro Andersson Kurt Andersson 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1995,672(2)
A method for the determination of aflatoxins B1, B2, G1, G2, M1 and Q1 in human urine has been developed. The 10-ml urine samples were automatically cleaned up on immunoaffinity columns and analysed by high-performance liquid chromatography (HPLC), including post-column derivatization with bromine and fluorescence detection. Average aflatoxin recoveries were: B1 103%, B2 106%, G1 98% and G2 96% in the range 6.8–73 pg/ml of urine and M1 103% and Q1 100% in the range 18–97 pg/ml of urine. The relative standard deviations were all between 1% and 21%. The determination limits of aflatoxins in urine were 6.8 pg/ml for B1, B2, G1 and G2 and 18 pg/ml for M1 and Q1. 相似文献
117.
Sandra Irene Pitta-Alvarez Ana María Giulietti 《In vitro cellular & developmental biology. Plant》1995,31(4):215-220
Summary
Brugmansia candida hairy roots, obtained by infection withAgrobacterium rhizogenes LBA 9402, exhibit, after subculturing in liquid media, a tendency towards dedifferentiation. It has been found that the following
strategies can be applied to inhibit this dedifferentiation and preserve normal root morphology: (a) lowering both the mineral
and sucrose concentration in the media employed so as to diminish osmotic stress (a condition to which these roots appear
to be particularly susceptible); (b) employing antiauxins in appropriate concentrations; and (c) maintaining the hairy roots
on solid media prior to use in production processes in liquid media. The first strategy suggested does not favor alkaloid
productivity, but in this case a two-step method could be attempted: biomass with normal root morphology could be obtained
in a first stage using low sucrose concentrations, and in a second stage, sucrose could be increased in order to achieve higher
productivity. In all the clones ofB. candida obtained, alkaloid production was biased towards scopolamine. 相似文献
118.
Abstract. The Argentine Chaco is a mosaic of grassland and open forest habitats maintained by natural disturbance activities such as fire. Since the introduction of domestic livestock and other human activities, the balance of this mosaic has been significantly altered, both in plant species and structural composition. This study focuses on the impact of such changes on the diversity of ground-dwelling arthropods within semi-arid Chaco forest. Quantitative measures of habitat structure and arthropod diversity were taken in forest areas previously subjected to grazing, logging and ploughing. Results indicated that arthropod diversity was smaller on sites with reduced structural complexity, with marked changes in arthropod family composition. The habitat components relating to plant architectural and vertical diversity were particularly influential on arthropod diversity. The guild size ratio of predatory to non-predatory arthropods also differed significantly between habitats suggesting a change in the resource base available to some groups. The latter suggests a shift in the functional organisation of the forest ecosystem which could have important repercussions for the diversity of other trophic levels. 相似文献
119.
A Primary Linkage Map of the Porcine Genome Reveals a Low Rate of Genetic Recombination 总被引:12,自引:0,他引:12
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H. Ellegren B. P. Chowdhary M. Johansson L. Marklund M. Fredholm I. Gustavsson L. Andersson 《Genetics》1994,137(4):1089-1100
A comprehensive genetic linkage map of the porcine genome has been developed by typing 128 genetic markers in a cross between the European Wild Boar and a domestic breed (Large White). The marker set includes 68 polymerase chain reaction-formatted microsatellites, 60 anchored reference markers informative for comparative mapping and 47 markers which have been physically assigned by in situ hybridization. Novel multipoint assignments are provided for 54 of the markers. The map covers about 1800 cM, and the average spacing between markers is 11 cM. We used the map data to estimate the genome size in pigs, thereby addressing the total recombination distance in a third mammalian species. A sex-average genome length of 1873 +/- 139 cM was obtained by comparing the recombinational and physical distances in defined regions of the genome. This is strikingly different from the length of the human genome (3800-4000 cM) and is more similar to the mouse estimate (1600 cM). The recombination rate in females was significantly higher than in males. 相似文献
120.
Reinard Thomas; Sprunck Stefanie; Altherr Sandra; Jacobsen Hans-Jorg 《Journal of experimental botany》1994,45(11):1593-1601
A monoclonal antibody of IgM-type (TIM-11B2) was screened froma hybridoma library. The antibody recognizes a 40 kDa glycoprotein,p40, with high specificity. This protein was detected in allplant species examined so far and was found to be located bothsolubly and ionically-bound within the primary cell wall. The strongest immunobiochemical signals of p40 were found intissues undergoing elongation growth, whereas in other tissuesonly a faint signal could be detected. Those included the non-elongatingparts of different seedlings, such as the apical part of monocotprimary leaves or the leaves of dicots grown in light. Inhibitionof pea epicotyl growth by white light irradiation resulted ina strong decrease of the immunostain signal. On the other hand,induction of rapid coleoptile growth in rice seedlings inducedby submergence resulted in a strong increase of the immunobiochemicalsignal of p40. Time-course studies on the expression of p40during protoplast regeneration revealed that p40 is apparentlynot involved in cell wall formation. The hypothesis that p40is characteristic for tissues with the ability for elongationgrowth is discussed. Comparison of biochemical data and location of p40 with proteinsdescribed up to now indicate that this glycoprotein has notbeen characterized before. Key words: Cell wall protein, elongation growth, monoclonal antibody 相似文献